Hydraulic elevator leveling system



May 31, 1966 Filed April 10, 1964 R. F. MARTIN HYDRAULIC ELEVATOR LEVELING SYSTEM 2 Sheets-Sheet 1 USR USRB

UST

M4 URI INVENTOR RICHARD F. MART/N ATTYS.

May 31, 1966 R. F. MARTIN 3,253,579

HYDRAULIC ELEVATOR LEVELiNG SYSTEM Filed April 10, 1964 2 Sheets-Sheet z PM 1 FI6.5

4 T/IZ 99 I25 I 3 1 FIG.3

United States Patent M 3,253,679 HYDRAULIC ELEVATOR LEVELING SYSTEM Richard F. Martin, Rock Island, Ill., assignor to Montgomery Elevator Company, a corporation of Delaware Filed Apr. 10, 1964, Ser. No. 358,864 9 Claims. (Cl. 187-28) This invention relates to 21 leaving system for hydraulic elevators which is operative as a car makes its approach to and stpps at a floor when it is traveling-upward.

Modern hydraulic elevators are operated at relatively high speeds, and when the higher modern day speeds .are combined with various changes in elevator and valve construction they tend to cause an elevator to stop suddenly and with quite a jar to the passengers. Factors which contribute to the sudden and rough stops include relatively lighter sheaves and belts, smaller pump motors with relatively light rotors, and better packing of the ram so that it moves more freely.

The conventional procedure for stopping a hydraulic elevator traveling in the up direction has been to first bypass a percentage of the hydraulic fluid so as to bring the elevator down to a leveling speed of from 3 to or feet per minute, bring the car nearly to floor level, stop the pump entirely and let the car coast to the floor level. It is quite apparent that with this system for stopping the car if the motor had a relatively heavy rotor and the sheaves and belts were relatively heavy their inertia would necessarily cause the elevator to coast to a stop rather gradually. Furthermore, if car movement was relatively retarded by packing around the ram it would tend to have a cushioning effect in the stopping of the car.

On the other hand, with very little inertia effect in the modern sheaves, belts and rotors, and with the car quite free to move because of improved packing around the ram, the elevator car tends to stop suddenly and with quite a jolt when the pump is stopped.

The problem is somewhat aggravated by the fact that certain of the modern elevator control valves which give a very stable up leveling speed and improved general operation over previously available valve equipment do tend to permit a car to stall out during up leveling unless the leveling speed is about 15 feet per minute. At an up leveling speed of 15 feet per minute and very little inertia in the system, the step can be excessively rough and jolting to passengers. Rough stops are particularly undesirable in hospital installations where many hydraulic elevators are now in use because of their operating characteristics.

In accordance with the present invention, the elevator is not stopped at floor level by stopping the pump motor and permitting it to coast to a stop. Instead, an adjustable metering valve with a solenoid control is placed in parallel with the main valve which controls the starting of the elevator for up travel and the leveling speed of the elevator. When the elevator reaches the stopping point at which the pump motor would have been stopped in any conventional installation, the solenoid control for the metering valve is opened so as to bleed a predetermined percentage of the hydraulic fluid from the main valve control chamber and pilot system so as to reduce the oil flow below the stalling level, thus stalling the elevator car hydraulically while the pump continues to operate. Preferably a time switch is used on the pump motor circuit so that a predetermined period of time after the metering valve solenoid operates to stall the elevator hydraulically the pump motor is stopped and the system is readied for a new operation.

The invention is illustrated in a preferred embodiment in the accompanying drawings in which:

FIG. 1 is a top plan view of the valve arrangement of the present invention;

325mm Patented May 31, I966 FIG. 2 is an end elevational view taken from the left of FIG. 1;

FIG. 3 is a longitudinal vertical sectional view of the main up travel control valve, taken substantially as indicated along the line 33 of FIG. 2;

FIG. 4 is a longitudinal vertical central sectional view of the solenoid valve for controlling operation of the bleed circuit;

FIG. 5 is a section taken substantially as illustrated along the line 5-5 of FIG. 1 to show the metering valve of the bleed circuit; and

FIG. 6 is a wiring diagram for the electrical controls that control operation of the system.

Referring to the drawings in greater detail and referring first to FIGS. 1 and 2, the present up leveling control system includes a main up travel control valve indicated generally at 10, an adjustable metering valve indicated generally at 11, and a two-way solenoid valve indicated generally at 12 which controls the flow of hydraulic fluid through the metering valve :11. The system also includes the conventional reservoir R and pump P (illustrated diagrammatically and out of scale in FIGS. 1 and 3), and a hydraulic cylinder and ram assembly C with the ram surmounted by an elevator car C1 (the ram and car are shown diagrammatically and out of scale in FIG. 3). i

Referring now particularly to FIG. 3, the main control valve 10 includes a body casting 13 having a fitting 14 to receive a fluid inlet 15 from the pump P, and a threaded hollow closure 16 to receive a pipe 17 by means of which fluid which passes through the main control valve 10 may be returned to the reservoir R. The inlet pipe 15 for the main control valve 10 branches from a main elevator operating line 18 which connects the pump P directly with the cylinder C below the ram. Thus, it is apparent that the main control valve 10 acts as a by-pass for returning hydraulic fluid directly to the reservoir instead of permitting it to pass through the cylinder of the elevator system.

The particular up control valve 10 illustrated in FIG. 3 is a. standard, commercially available elevator service valve that is manufactured and sold by Elevator Equipment Company of Los Angeles, California, as its type VU-2 valve. Within the valve body 13 is a control piston chamber, indicated generally at 19, thatincludes a rear piston control portion 20 and a threaded recess 21 into which is screwed a guide insert 22. Communicating with the control plunger chamber 19 is a return chamber 23 within which is a perforated sleeve 24 having a central imperforate baffle 25 which forces fluid flow through the chamber 23 to be generally as indicated by the curved arrows which pass back and fort-h through the perforated screen wall.

A main control piston 26 is mounted for reciprocal movement in the control chamber 19 and has an O-ring turn spring 29 bears upon a shoulder on the cup and upon the front of the piston 26 and normally urges the piston to its extreme open position where hydraulic fluid from the line 15 which enters a forward chamber portion 30 of the piston chamber 19 may pass between the spaced fingers of the plunger guide 28, through the hollow guide 22 and into the return chamber 23. The control chamber 19 is closed at its rear end by a cap 31 having a central bore within which is a piston stop pad 32 that limits the movement of the piston toward open position and that may be adjusted by means of a set screw 33. When the control piston 26 is in the position illustrated in FIG. 3

the main fluid line 18 is in direct communication with the reservoir R through the line 15, the forward chamber portion 30, the return chamber 23, and the line 17. The main control valve is in the position illustrated in FIG. 3 only when the pump is not operating.

'In addition to the main piston assembly the control valve 10 includes a piloting system the operation of which is controlled by a solenoid pilot valve, indicated generally at 34, a pressure regulator piston assembly indicated generally at 35, and a start adjusting needle valve assembly indicated generally at 36.

From the forward portion of the piston chamber a diagonal piston control bore 37 communicates with a pressure bore 38 by which fluid may enter the chamber 20 behind the piston, and also with a piloting bore 39 which communicates with the solenoid pilot valve assembly 34. It is apparent that as soon as the pump is started, there is a flow of fluid through the bore 37 and the bore 38 to the chamber 20 behind the piston and the fluid pressure on the back of the piston compresses the spring 29 to seat the piston valve seat 26a upon the cup valve seat 22a. This closes the by-pass and causes the full pumpoutput to pass to the elevator cylinder C.

The rate at which the piston moves from its open to its closed position depends upon the setting of the control valve 36, which will now be described in detail. A generally cylindrical core 40 has a threaded portion 41 by means of which it screws into the inclined bore 37, and a central fluid passage 42 that communicates through a cross bore 43 with the bores 38 and 39 has an enlarged inner end 44 affording a seat 45 for a ball valve 46 that is held against the seat by a spring 47. A ball adjusting stem 48 is threaded at 49 and has an external knurled head 50 by which it may be manually adjusted. Thus the stem 48 determines the amount of space between the ball 46 and the seat 45 and controls the rate at which fluid from the piston control bore 37 enters the pressure bore 38.

Referring now to the pilot control valve assembly 34, the body 13 of the control valve 10 is seen to have a well 51 with which the pilot bore 39 communicates, and a threaded recess 52 in the bottom of the well 51 receives a threaded pilot valve core 53 that has a centralbore 54; while a thread 55 in the upper wall of the well 51 receives a nipple 56 in which is seated a guide shell 57 which is in spaced relationship to the core 53 to aflord a passage 57a between the pilot bore 39 and the bore 54. A spring 58 seats on a spring flange 53a of the core 53 and extends upwardly into contact with the lower end of a needle valve plunger 59. A valve head 60 at the bottom of the plunger 59 is adapted to rest upon a valve seat 61 at the upper end of the bore 54, so that downward movement of the needle valve plunger closes the upper end of the bore 54 to out 01f communication between the pilot bore 39 and pilot bore extensions 62 and 63 which are formed in the valve body 13 and communicate with a portion of the pressure control piston assembly 35.

The pilot needle valve 60 is normally open, and a solenoid 64 that is carried in a casing 65 may be enervgized to close the pilot needle valve 60. A solenoid cover 66 surmounts the shell 65, and a solenoid spring 67 beneath a cap 66 bears upon the solenoid 64. A thread- 4 ed opening 66a in the cap 66 is for the solenoid circuit connections.

Referring now particularly to the pressure regulator assembly 35, the valve body 13 is provided with a well 68 the upper end of which communicates with the pilot bore extension 63, and at the bottom of the well 68 is a hole 69 that communicates with the fluid discharge chamber 23. A thread 70 in the upper portion of the well 68 receives a fitting 71 in the bottom of which is a recess 72 which is threaded to receive a hollow annular plug 73. A valve plunger 74 is held up by a plunger spring 75 and its upper end extends into a recess 76 in the top of the fitting 71.

At the upper end of the well 68 the valve body 13 has a recess 77 which surrounds the projecting upper end of the fitting 71, and a planar surface 78 of the valve body surrounds the recess 77 to receive a pressure regulator body 79 the lower end of which rests upon a gasket 80 to define a pressure regulator chamber 81, and a pressure regulator piston 82 is provided with a U-ring 83 which provides a seal between the piston and the inner wall of the regulator body 79. A bore 84 connects the chamber 81 with the fluid outlet chamber 23 so that the pressure regulator plunger 82 is subjected to the pressure of fluid within the chamber 23.

The pressure regulator plunger 82 has a central upstanding hollow boss 85 which serves as a guide for a plunger regulator 86 the lower end of which extends into the recess 76 in the top of the fitting 71 and bears upon the upper end of the plunger valve 74. Surrounding the hollow boss 85 and guided thereon is a spring guide 87 that is surmounted by a pre-set spring 88 and acts as a guide for a regulator spring 89. A threaded boss 90 at I the top of the regulator body 79 receives a screw cap 91 which may be rotatably adjusted to change the force with which regulator spring 89 bears upon the. pressure regulator piston 82. The threaded pressure regulator cap 91 has a central hollow boss 92 which carries a nut 93 into which is threaded an adjusting screw 94 that is integral with the plunger regulator 86. Surrounding the regulator cap 91 is a regulator indicator 95 that has an indicator screw 96.

The operation of the pilot circuit of the valve 10 is as follows: The pilot circuit needle control valve 60 is normally open, so that the chamber 20 behind the main control piston 26 is in communication with the fluid discharge chamber 23 through the bores 38 and 39, the passage 57a inside the spring guide shell 57, the bore 54, the continuation pilot bore 62 and 63, the recess 72 in the bottom of the fitting 71, and the hole 69. When the pump is started the solenoid 64 is energized to close the pilot needle valve 68 and isolate the rear chamber portion 20 from the fluid discharge chamber 23 so that pressure from the pump is applied to the rear of the main control piston 26 to close the by-pass through the fluid return chamber 23 and the conduit 17. When the elevator car reaches the leveling zone approaching a floor where it is'to stop, the solenoid 64 is deenergized, thus opening the pilot control needle valve 60. This again places the rear chamber 20 in communication with the fluid return chamber 23, and the pressure drop behind the main control piston 60 depends upon the setting of the pressure regulator piston 82 and the plunger 74. This, therefore, controls the extent to which the main control piston 26 is moved toward open position by the spring 29, and thus the rate at which fluid is by-passed to the reservoir. The pressure regulator cap 91 can be adjusted so far down that the car will stall completely when the pilot control needle valve 60 is opened by deenergization of the solenoid 64. However, for normal operation the pressure regulator cap 91 is backed off until the by-pass of fluid permits a leveling speed of about 15 feet per minute. Adjustment of the plunger valve 74 by turning the adjusting screw 94 changes the setting of the plunger 74 so as to control the rate at which the main piston 26 is moved toward open position by the spring 29, and thus determine the rapidity with which the car changes from normal up traveling speed to leveling speed.

At the end of the leveling zone in normal operation of the commercial UV-2 valve the pump is stopped and the car coasts to a halt at the floor level as the spring 29 moves the main control piston 26 to its fully open position. The entire system is then in condition for a new up start.

In accordance with the present invention, however, the pump is not stopped when the elevator reaches the top of the leveling zone. Instead, the two-way solenoid valve 12 is opened so as to by-pass fluid at a controlled rate from the chamber portion 20 behind the main con trol piston 26 through a bore 97 and a conduit 98 into the metering valve 11 which is connected by a nipple 99 with the inlet of the two-way solenoid valve 12. Thence the fluid passes through a conduit 100 into the fluid return chamber 23 from which it returns to the reservoir. By adjusting the metering valve 11 the rate at which fluid is bled from the chamber 20 may be set so that the elevator car stalls hydraulically with the pump operating, thus providing for a soft, cushioned stop of the car at the floor level. Continued operation of the pump is afforded by a. time delay relay which is energized at the same time as the two-way solenoid valve 12, with the time delay calculated to cut out the pump motor a few seconds after'the car has been stopped by the hydraulic stalling action of the bleed circuit through the metering valve 11.

The two-way solenoid valve is also a standard commercially available device that is marketed by Automatic Switch Co. of Florham Park, New Jersey, through its Asco Valve Division, and presumably comparable valves are also manufactured and sold by other companies. Turning now to FIG. 4 of the drawings, the two-way solenoid valve 12 includes a body 101 and a bonnet 102 which are bolted together. The body defines an inlet chamber 103 and an outlet chamber 104 which are separated by a wall 105; and threaded bosses receive the inlet conduit 99 and the outlet conduit 100. A wall 105 connects continuously with an internal flange 106 to provide a continuous valve seat 107 for a valve member 108 that is carried in the bonnet 102. When the valve 108 is in the position of FIG. 4 there is no fluid flow through the valve 12, while elevation of the valve member 108 opens the valve for fluid flow from the chamber 103 to the chamber 104. A tight seal on the valve seat 107 is obtained by a valve washer 109 that is seated in the bottom of the valve plunger 108.

Movement of the valve plunger 108 between its closed and open positions is controlled by a pilot solenoid valve system, said system including a bore 110 in the bonnet 102 which affords communication between the inlet chamber 103 and the space above the valve plunger 108; while a bore 111 in the plunger108 connects the space above the valve plunger with a pocket 112 that is below one side of the valve plunger.

In the bonnet 102 is a pilot bore 113 with a valve seat 114 at its upper end to receive the conical tip 115 of a valve plunger 116 the position of which relative to the valve seat 114 is determined by the energization or deenergization of a solenoid 117. A solenoid housing 118 surmounts the valve bonnet 102.

When the solenoid is deenergized as seen in FIG. 4, fluid is in the chamber 103, the bore 110, the space above the plunger 108, and the bore 111 and pocket 112. A valve spring 119 and pressure seat the valve.

Energization of the solenoid 117 elevates the pilot control plunger 116 to open the pilot valve 115, permitting fluid to pass through an opening 120 and through the 'pilot bore 113 into the fluid discharge chamber 104, and

the pressure under the valve plunger 108 raises it, permitting fluid to pass from the inlet chamber 103 through the outlet chamber 104 and the conduit 100 to the fluid return chamber 23 of the control valve 10.

As seen in FIG. 5, the metering valve 12 is a very common type of manually adjustable needle valve that has a housing 121 with an inlet stem 122 and an outlet stem 123 at right angles to each other, both said stems being threaded to receive the conduits 98 and 99, respectively. The stems 122 and 123 have fluid bores 124 and 125, respectively, and a needle valve member 126 is threaded at 127 and has a finger piece 128 by means of which it may be adjusted in a packing gland 129 so as to accurately control the flow of fluid from the passage 124 into the passage 125. Accordingly, when the two-way solenoid valve 12 is opened it permits fluid to bleed from the chamber 20 behind the control piston 26 at a rate which is deter- 6 mined by the setting of the metering valve 11, and the latter is set so that the ratio between fluid pumped to the cylinder C and that returned to the reservoir R will cause the elevator car to stop at the floor level by stalling hy draulically.

Referring now to FIG. 6, which shows the electrical control circuitry for starting, leveling and stopping the elevator in the form of a conventional across the line wiring diagram, there are electric lines 130 and 131 across which the controls operate. Due to the extreme simplicity of the circuit it is thought that no key diagram is needed.

Up travel of the elevator is started only when a call for service is registered which requires travel in the up direction, and after the door is closed and its electric interlock in proper condition for car travel. At that point the pump motor starting contactor U closes, to start the pump, and at the same time the usual up direction signal relay which is in the known hydraulic elevator operating systems is energized to close a contact UR1 and open a contact UR2. Closing UR1 energizes the solenoid 64 of ,control valve 10 to close the pilot circuit valve 60. This causes pump pressure to close the control piston 26 completely. I

Operation of the circuit components when the car reaches the leveling zone is by switches and cooperating switch actuators which are on the car and in the hatchway. Conveniently such switches and actuators are of the type disclosed and claimed in Beck Patent 2,843,697. As shown in that patent there are vertically spaced magnetic switches on the outside of the car, and a vertical iron vane in the hatchway that charges the magnetic flux of the switch control magnets to actuate the switches in sequence as the elevator car approaches the floor. It is obvious that a series of switches may be operated in some known other way to energize and deenergize the circuit components.

When the car reaches the up leveling zone of a floor at which it is to stop, several things happen. First the up direction signal relay is deenergized, opening contact URI and closing UR2. This deenergizes the control valve solenoid 64 and thus opens the pilot circuit valve 60 to reduce elevator speed to about 15 f.p.m. At about the same time a magnetic switch on the car is actuated by a vane in the hatchway to energize a relay (not shown) having a normally open contact ULRI and a normally. closed con-tact ULR2. Closing ULRI energizes a timer UST and closes a normally open time delay contact USTD; and this in turn energizes a relay USR to close two normally open contacts USRl and USR2. Contact USTD is the type that remains closed for a predetermined time after UST is deenergized. Opening ULR2 prevents two way valve solenoid 117 from being energized for the time being, since ULR2 is in series with USRI and thus 117 would be energized by the closing of USRl were it not for the opening of ULR2. Closing contact USRl energizes an auxiliary relay USRB to open a normally closed contact USRBI, nd thus open the usual holding circuit to the pump motor starting contactor U, while closing contact USR2 closes a circuit through a normally closed down leveling contact DLC and a normally closed down contact D to provide a separate holding circuit to said contactor U.

When the car runs out of the up leveling zone the mag netic switch which closed to energize USR opens again, opening ULRI to deenergize UST and thus condition USTD to open when its set time runs out. ULR2 is again closed to energize the bleed circuit valve solenoid 117 to open the two way valve 12 and bleed fluid from con trol chamber 20, thus permitting control piston 26 to open far enough that the car stalls.

At 15 f.p.m. the car is moving inches per minute, or about an inch every /3 of a second. The car stalls out in no more than an inch of travel, and may be set to stall out in /2 inch /6 of a second) and still eliminate the jolt that would occur if the car were stopped by stopping the pump.

Contact USTD times out immediately after the car stalls to a stop; and timing open of said contact USTD deenergizes USR and thus re-opens the contacts USR1 and USR2, breaking the timed holding circuit for the pump motor contactor U and stopping the motor and pump. Spring contact USRl also breaks the circuit through ULR2 and thus deenergizes the valve solenoid 117 to close the bleed control valve 12. Stopping the pump takes the pressure off of control piston 26 and that piston opens fully in readiness for another operation. At the same time USRB is deenergized to restore conventional pump holding circuits so that the next demand for up service may start the sequence again.

While I have shown and described certain embodiments of my invention, it is to be understood that -it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In a hydraulic elevator system serving a plurality of floors, in combination: a hydraulic ram; an elevator car on said ram; a fluid reservoir; a pump to deliver fluid from the reservoir under pressure; a ram conduit for delivering fluid from the pump to the ram; a by-pass conduit for returning fluid from the pump to the reservoir; a control valve having a piston to selectively admit the full pump output either to the ram conduit or to the by-pass conduit; means for starting, the pump; means for applying pressure from the pump to the piston to move the piston and admit the full pump output to the ram conduit for elevating the ram at full speed; valve means for selectively conducting a first proportion or a second proportion of the fluid bearing on the piston to the by-pass conduit to move the piston to either of two diflerent positions, the first position being predetermined to reduce ram speed for leveling and the second position .being predetermined to stall the ram; means for actuating the valve means when the car reaches a leveling zone to conduct said first proportion of fluid to the by-pass conduit and reduce car speed for leveling; means for thereafter actuating the valve means to conduct said second proportion to the by-pass conduit to stall the car at the floor; and means for stopping the pump after the car stalls at the floor.

2. In a hydraulic elevator system serving a plurality of floors, in combination: a hydraulic ram; an elevator car on said ram; a fluid reservoir; a pump to deliver fluid from the reservoir under pressure; a ram conduit for delivering fluid from the pump to the ram; a by-pass conduit for returning fluid from the pump to the reservoir; control valve means between the pump and the by-pass conduit; said control valve means including a piston to selectively open and close the by-pass conduit; means to start the pump; means for applying pressure from the pump to the rear of the piston to close the by-pass conduit and elevate the ram at full speed; a pilot circuit and a bleedcircuit in parallel for selectively conducting two diflerent proportions of the fluid from behind the piston to the bypass conduit, the pilot circuit being adapted to reduce ram speed to a leveling speed and the bleed circuit being adapted to stall the ram; means for opening the pilot circuit when the car reaches a leveling zone of a floor at which it is to stop; means for closing the pilot circuit and opening the bleed circuit to stall the car at the floor; and means for stopping the pump after the car stalls at the floor.

3. The combination of claim 2 in which the bleed means includes an adjustable metering valve, and means for starting and stopping the flow of fluid through the metering valve.

4. The combination of claim 3 in which the means for starting and stopping the flow of fluid through the metering valve comprises a separate solenoid controlled valve.

5. The combination of claim 2 in which the means for stopping the pump includes a pump holding circuit, means for energizing said holding circuit when the bleed means is first opened, and means in the holding circuit for de-energizing the pump holding circuit a predetermined time after the metering valve is opened.

6. The combination of claim 2 that includes a primary electric operating circuit for the pump, relay means in said operating circuit for starting the pump, a secondary operating circuit in parallel with the primary circuit, a time delay means in the secondary circuit, and means actuated when the bleed means is opened for de-energizing the relay means in the primary operating circuit and energizing the secondary operating circuit'through the time delay means.

7. In a hydraulic elevator system serving a plurality of floors, in combination: a hydraulic ram; anelevator car on said' ram; a fluid reservoir; a pump to deliver fluid from the reservoir under pressure; a ram conduit for delivering fluid from the pump to the ram; a by-pass conduit for returning fluid from the pump to the reservoir; control valve means between the pump and the by-pass conduit; said control valve means having a by-pass control piston, spring means urging said piston toward open position to admit fluid to the by-pass conduit and means for admitting fluid from the pump to the rear of the piston to move the piston toward closed position; pilot means including a pilot control valve; and a pressure regulator for selectively conducting a predetermined portion of the fluid from behind the piston to the bypass so as to partially close the by-pass piston; means for starting the pump and closing the pilot control valve to close the piston and start the car up at normal full speed; leveling control means responsive to the upward approach of the car to a floor at which it is to stop, said leveling control means opening the pilot control valve to partially open the piston and reduce the speed of the car for leveling; a separate bleed circuit extending from behind the piston to the by-pass, said bleed circuit including metering means and a control valve; means operative as the car reaches a floor at which it is to stop for opening the control valve to bleed enough fluid from behind the piston to stall the car at the floor; and means for stopping the pump to fully open the control piston shortly after the car has stalled at the floor.

8. The system of claim 7 in which the bleed circuit metering means is adjustable to control the rate at which fluid bleeds through said bleed circuit.

9. The system of claim 7 in which the means for stop- References Cited by the Examiner UNITED STATES PATENTS 2,737,197 3/19 56 Jaseph 6052 X 3,057,160 10/1962 Russell 6052 HUGO O. SCHULZ, Primary Examiner. 

1. IN A HYDRAULIC ELEVATOR SYSTEM SERVING A PLURALITY OF FLOORS, IN COMBINATION: A HYDRAULIC RAM; AN ELEVATOR CAR ON SAID RAM; A FLUID RESERVOIR; A PUMP TO DELIVER FLUID FROM THE RESERVOIR UNDER PRESSURE; A RAM CONDUIT FOR DELIVERING FLUID FROM THE PUMP TO THE RAM; A BY-PASS CONDUIT FOR RETURNING FLUID FROM THE PUMP TO THE RESERVOIR; A CONTROL VALVE HAVING A PISTON TO SELECTIVELY ADMIT THE FULL PUMP OUTPUT EITHER TO THE RAM CONDUIT OR TO THE BY-PASS CONDUIT; MEANS FOR STARTING THE PUMP; MEANS FOR APPLYING PRESSURE FROM THE PUMP TO THE PISTON TO MOVE THE PISTON AND ADMIT THE FULL PUMP OUTPUT TO THE RAM CONDUIT FOR ELEVATING THE RAM AT FULL SPEED; VALVE MEANS FOR SELECTIVELY CONDUCTING A FIRST PROPORTION OR A SECOND PROPORTION OF THE FLUID BEARING TO EITHER OF TWO DIFFERENT POSICONDUIT TO MOVE THE PISTON TO EITHER OF TWO DIFFERENT POSITIONS, THE FIRST POSITION BEING PREDETERMINED TO REDUCE RAM SPEED FOR LEVELING AND THE SECOND POSITION BEING PREDETERMINED TO STALL THE RAM; MEANS FOR ACTUATING THE VALVE MEANS WHEN THE CAR REACHES A LEVELING ZONE TO CONDUCT SAID FIRST PROPORTION OF FLUID TO THE BY-PASS CONDUIT AND REDUCE CAR SPEED FOR LEVELING; MEANS FOR THEREAFTER ACTU- 